A common use for a chipper is to open the faces of a log. A log is generally round in shape and lumber production from the log requires a flat surface. For example, the first board to be cut may require 3-31/2 inches of flat surface width at its minor face. Thus, the first operation will likely remove the log material at two opposed sides, i.e., outside of a vertical chord through each side of the log, the height of the vertical chord representing the width dimension of the minor face of the board to be cut. The material so removed is valuable as chips for making pulp. It is, therefore, desirable to cut the material into chips of a generally consistent size. Whereas the log material to be removed may be sawed off and then chipped, that requires two operations. Chippers of the present invention are designed to produce the desired open flat surfaces or faces and in the process to remove the side material from the log as chips.
A chipper includes a rotating disk on which multiple blade holders are peripherally mounted. Chipper blades are removably and adjustably mounted in the blade holders. The holders are massive steel members designed to withstand the shock and abuse of high speed impact when cutting into a fast moving oncoming log.
Two inter-related problems are addressed by the present invention. The holder includes support legs that are anchored to the periphery of the disk. A blade holding body portion is spaced above the disk periphery and is supported at its ends by the support legs. An opening is provided under the body portion and between the legs to allow chips to flow past the blade and blade holder. However, a substantial portion of the chips strike the outer support leg and are damaged insofar as being desirable for chip production. This damage has been heretofore considered unavoidable as the support is considered necessary for retaining the rigid resistance to the impact encountered by the holder.
The second problem also relates to chip flow. The two blade portions are abutted together to make a corner or bend. The corner area is a high impact area and although the joint is tightly formed, wood strands are driven into the corner and become wedged between the blade portions. This interferes with the cutting action and can mar or groove the opened face being formed on the log. This requires further operation down stream with additional material having to be removed.